#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
int fun(int a)
{
	if (a <= 2)
	{
		return 1;
	}
	else
	{
		return fun(a - 1) + fun(a - 2);
	}
}
int main()
{
	int a = 0;
	scanf("%d",&a);
	int z=fun(a);
	printf("%d",z);
	return 0;
}
